1. Technical Field
The present invention relates to a time information receiver, a radio wave correction timepiece, and a time code type determination method.
2. Related Art
Some radio wave correction timepieces used in recent years receive a radio wave containing time information (long-wave standard radio wave), automatically correct the time by using the time information, and display the corrected time.
As a radio wave correction timepiece of this type, there is a disclosed multiband-supporting radio wave timepiece capable of receiving a variety of standard radio waves transmitted in Japan, European countries (Germany, England), North America, and other countries (JP-A-2013-19723).
To determine a time code in a received standard radio wave in a case where the frequency of the standard radio wave differs from those of the other standard radio waves, for example, in the case of DCF77, which is German standard radio wave, the time code of the received radio wave can be determined by identification of the reception frequency.
On the other hand, some of the variety of standard radio waves described above have the same frequency. Specifically, JJY60, which is a standard radio wave transmitted from a transmitting station in Kyushu, Japan, WWVB, which is an American standard radio wave, and MSF, which is a British standard radio wave, are each a radio wave of 60 kHz. Therefore, when a standard radio wave is received with the reception frequency set at 60 kHz, it is necessary to further analyze the time code to determine the type of the radio wave.
To this end, in JP-A-2013-19723 described above, a rising edge cycle measurement part that measures the rising edge cycle of a demodulated signal based on a standard radio wave and a low level width measurement part that measures a low level signal width are provided, and the standard radio wave is measured for, for example, 10 seconds. In a case where the low level width measurement part determines at least once that the low level signal width is 100 ms, the type of the standard radio wave is determined to be MSF. In a case where the count of occurrences in which the low level signal width is 100 ms is 0, the type of the standard radio wave is determined to be JJY60 when the count of occurrences in which the rising edge cycle measurement part determines that the rising edge cycle is 1 second is greater than or equal to a threshold (9 in 10-second measurement, for example), and the type of the standard radio wave is determined to be WWVB when the count described above is fewer than the threshold.
However, in a case where the standard radio wave has a small electric field intensity, or in a case where the waveform of the standard radio wave varies due to noise, the rising edge cycle of the demodulated signal based on the standard radio wave varies, and the number of 1-second-cycle rising edge cycles may be fewer than 9 even when the standard radio wave JJY60 is being received, resulting in wrong determination.
Further, in the case where the standard radio wave has a small electric field intensity, variation in the signal width causes a 200-ms low level signal width signal of the standard radio wave WWVB to narrow, and the 200-ms signal is possibly wrongly determined to be a 100-ms signal.